NAD+ enhancer modulates macrophage phenotype
into an anti-inflammatory character
LMT503, a novel NAD+ enhancer, was discovered by Lmito
Therapeutics in an attempt to find IBD therapeutic candidates via
modulation of macrophages (Figure 1a). NAD+ synthesis
in macrophages has been reported to contribute to immune suppressive
functions by increasing oxidative phosphorylation (Minhas et al., 2019).
LMT503 works as an efficient substrate for NQO1 which can increase
cellular NAD+/NADH ratio in BMDMs (Figure 1b). To
investigate the effect of LMT503 on inflammatory macrophages, BMDMs were
stimulated with LPS and then treated with LMT503. LMT503 treatment
decreased levels of inflammatory signature molecules TNF-α and iNOS
(Figure 1c) but increased anti-inflammatory signature molecules Arg1 and
IL-10 (Figure 1d) in BMDMs. Sirtuins, a class III histone deacetylases
dependent on NAD+, can inhibit NLRP3-inflammatory
pathways of macrophages and favor anti-inflammatory polarization of
macrophages (Pan, Dong, Huang, & Fang, 2022; S. Y. Park et al., 2017).
LMT503 treated BMDMs showed increased expression of Sirtuins 1, 3, and 6
(Figure 4e). Upregulated expression of GATA3 is known to induce
anti-inflammatory polarization of macrophages (Faas et al., 2021).
Treatment with LMT503 increased the expression of GATA3 in BMDMs (Figure
1f). However, pro-inflammatory cytokine IL-1β level was decreased after
LMT503 treatment (Figure 1g). Human monocytic THP-1 cells and human
monocytes also showed increased levels of anti-inflammatory markers Arg1
and IL-10 (Figure 1h,i). These data suggest that LMT503 treatment could
induce shift of pro-inflammatory macrophages to an anti-inflammatory
character.